See all those extra exclamation points? Those are there because we know (thanks to neuroscientist Wolfram Schultz’s research) that surprise intensifies our emotions by about 400 percent.

And according to Mellers et al., a surprising $9 win is more enjoyable than an expected $17 win (that’s around 53 percent more bang for your buck).

Given these findings, it seems a shame to ever let people know when they should be expecting something pleasant. But before you unleash the full extent of your surprise skill, there’s a catch: not all people react to surprise in the same way.

At least three variables affect whether your surprises will lead to shrieks of delight, shrieks of anger, or an uncomfortable silence:

Culture: Culture might play a big role in the success of your surprise. For example, while Westerners generally love surprise gifts, gifts tend to make East Asians uncomfortable. However, surprises attributed to good luck make East Asians even happier than Westerners. Do some sneaky investigating about your surprise recipient's preferences before launching your surprise scheme.

Sensitivity: Some of us are more easily startled than others (a fact my husband relishes when he gets me to scream every time he sneaks up behind me or jumps out from behind a corner). Since surprise intensifies emotion, too much intensity may be uncomfortable for some of us. Introverts might still love surprises, but aim for small delights rather than big bangs.

Tolerance for Ambiguity: Many of us crave certainty and control. Since surprise catches us off guard, it makes some people feel unpleasantly vulnerable. For folks with low tolerance for ambiguity: give clues leading up to the surprise instead of keeping them completely in the dark, make sure the surprise isn’t embarrassing, and share in the experience together.